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Operation
4.4,2
Transistor testing
A
matrix system
for testing
DC
parameters
of
transis-
tors
is
shown
in
Figure
4-7.
This
system
uses
two
Source
Measure
Units
(SMU). There
are three
SMUs
available
hrom
Keithley;
the
Model
236 Source
Measure
Unit,
Model
237
High
Voltage
Soturce
Measure
Unit
and
Model
238
High
Current Source
Measure
Unit.
Keep
in
mind
that
if
using the
Models
237
(high voltage
capability) or
238
(high current
capability),
do
not
ex-
ceed
the
maximum
signal
levels
of the
matrix
card.
Maximum
allowable
DC
signals are
llOV and
lA,
SOW
with
resistive load.
This
system
tests
three
transistors,
but can be
expand-
ed
to
test
more by
simply using
additional
Model
7012
matrix
cards.
The Model
7001
will
accommodate two
matrix
cards.
Daisy-chaining
six
Model
7001s
expands
the
system
to
12
matrix
cards
allowing 36 or
more
tran-
sistors to
be
tested.
NOTE
The
Model
7012
is
a general
purpose
matrix card
and
cannot
be used
to
check PEXs
or
transistors that
have
high
gam
or
low
power.
To
test
these
devices,
a matrix card
with
low
offset
current
and
high
isolation characteris-
tics
must
be
used.
Figure
4-7
Transistor
testing
4-10
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